1. Field of the Invention
The present invention relates to a rear portion structure of a saddle-type vehicle.
2. Description of Background Art
In a saddle-type vehicle, a swing arm can be swingably supported by a vehicle body frame and a rear wheel can be rotatably supported by the swing arm. A drive chain is widely used as means for transmitting a drive force of a power unit to the rear wheel in such a saddle-type vehicle. The drive chain is entrained about a drive sprocket provided on the power unit and a driven sprocket mounted on the rear wheel. Since the driven sprocket swings in the vertical direction, the drive chain also swings in association with a swinging motion of the swing arm. It is known to use a chain roller for preventing the drive chain from coming into contact with vehicle-mounted components when the vehicle-mounted components are arranged in the vicinity of the drive chain (see JP-A-2009-179236 (FIG. 3), for example).
As shown in FIG. 3 in JP-A-2009-179236, a chain roller (93) (reference numerals in parentheses indicates reference numerals in JP-A-2009-179236, hereinafter) is mounted on an inner side surface (4c) of a center frame on the upper side of a portion in the vicinity of a pivot shaft (26) via a shaft (95).
When a drive chain (19) is moved more than a predetermined extent, the drive chain (19) comes into contact with the chain roller (93), so that the drive chain (19) may be prevented from coming into contact with electrical components (91, 92) or the like.
Incidentally, the drive chain (19) does not swing in the vertical direction at portions of the drive sprocket and the driven sprocket, but is displaced (deflected) significantly in the vertical direction at an intermediate portion between the drive sprocket and the driven sprocket.
Therefore, the susceptibility of the effects of the swinging motion or the deflection of the drive chain are reduced by arranging the vehicle-mounted components considering the deflection of the drive chain in the rear portion of the vehicle. However, as a consequence, since a space for arranging the vehicle-mounted components is limited in the rear portion of the vehicle, a larger space for arrangement of the vehicle-mounted components has been desired.